The winner of the April 30 Democratic primary will be heavily favored to win the seat of former Sen. John Kerry, D-Mass., who is now secretary of State. In this poll, both Markey and Lynch led their potential GOP opponents for the June 25 special election by wide margins.

Former U.S. Attorney Michael Sullivan led with 28 percent among likely GOP primary voters, followed by state Rep. Dan Winslow with 10 percent and Gabriel Gomez, a private equity investor and former Navy SEAL, with 8 percent. Forty-six percent were undecided.

The poll of 610 likely voters was conducted March 19-21. The full sample had a 4.1-point margin of error, but the margins of error for the primaries were not provided.